Older women who have had breast cancer surgery have a greater risk of the cancer returning if they delay their post-surgical radiation treatment, according to Dana-Farber Cancer Institute scientists.
The study, which involved more than 18,000 women aged 65 years and older who had breast cancer, found that those who started radiation treatment more than 6 weeks after breast-conserving surgery were more likely to have a local recurrence than those whose radiation treatment started within 6 weeks of surgery.
Rinaa Punglia, MD, MPH, a radiation oncologist at Dana-Farber and Brigham and Women’s Hospital and the study’s lead author, said she and her colleagues conducted the research to address scientifically the debate about the “appropriate interval between surgery and radiation treatment, or radiotherapy, and its impact on treatment outcomes,” according to a news release.
The researchers reviewed Medicare database records of 18,050 women with early stage breast cancer to assess whether the timing of when radiotherapy started following surgery affected outcomes. These women were treated between 1991 and 2002 with lumpectomy and radiation, but not chemotherapy. Thirty percent of women began radiotherapy 6 or more weeks after surgery.
For the overall group, slightly more than 4% of the women experienced a local recurrence. The risk increased to about 5%, approximately a 19% jump, when the surgery-radiotherapy interval was longer than 6 weeks. The researchers found that there was no “threshold” at which the risk suddenly rose – it increased incrementally day by day.
“There isn’t a large difference between 43 days instead of 41,” Punglia said. “The day-to-day risk increase is small.”
The rise in breast-conserving surgery in the past two decades has fueled greater demand for radiotherapy, and might be one cause of longer waiting times. The study revealed more delays in areas such as the Northeast, where the procedure is more common, and fewer delays in the southern states, where breast-conserving surgery
Although the study focused on older women, the findings have implications for younger women.
“It’s possible that the increased risk we identified in older women could be magnified in younger women, whose tumors are biologically different and tend to be more aggressive,” Punglia, who is also an assistant professor of radiation oncology at Harvard Medical School, said.